Does anyone know if there is much penalty in the medium-long term for late submissions of the thesis?

I currently have an extension to my initial three years but that extension expires early in the new year. I don't think I'm going to be able to finish a full draft between now and Christmas which will make timely submission virtually impossible. My university is very strict on submission - I had to go through a full end of year evaluation before being granted my current extension and once you reach the end of year five the handbook says they can fail you - but I think having qualified for a fourth year I will be able to continue either through a further minor extension or by paying up writing up fees to cover the rest of the academic year. But I was wondering beyond falling foul of my institutions increasingly fixed submission rules are there further consequences to finishing as a fourth rather than third year student? Will it affect my ability to bid on funding or in applying for post-doc work? Knowing that different universities have very different rules on submission will this be seen as a sign I'm a slacker who can't be trusted or just someone who needed a little longer to get the job done or will it not even raise an eyebrow at all?

Regardless of what corrections or whatever are recommended at viva having a PhD is having a PhD, right?

As long as you get your university to approve it, it will make no difference whether you took 3 or 4.5 years to complete your thesis. No-one will ever know, or care, to be honest. Look at the length of time that elapses between submission and graduation - for me that will be 7 months, for others it can be 1 to 1.5 years and probably longer.

Most UK universities have a 4 year submission deadline as standard anyway.

Like you said, a PhD is a PhD.

yeah what tree of life said.
i am in the humanities and the majority of folks at my uni (a not awful russell group) need the full 4 years and an extension. no one is batting an eyelid. i know only two people who didn't need an extension and no-one managed to do it in the three years, all needed the full writing up year. i will submit after 4 years and a health-related extension of 3 months.
i have also been told by an academic that some institutions prefer it if people spend more time on their phd as they associate this with better quality. at another department people get told to slow down, that goes especially for the better students. to someone not so good they say: 'ok get it out of the way and be gone' and someone better gets encouraged to spend more time on refining stuff. someone from my department almost took 5 years over it and is on her third postdoc. she had very nice postdocs. so i wouldn't worry, just keep an eye on the regulations.

Good to know. I think nearly everyone I know from other places seem to have a freer time than my place and their new 'three years or you better have a bloody good reason' policy of whipping PhDs through on time.